This invention relates in general to air filters, and more particularly to an air filter for use on an apparatus wherein the amount of available space for the filter is limited. Moreover, the filter of the present invention must be strong in construction and should preferably be capable of supporting the weight of a man thereon. Additionally, the filter should be simple in construction, such that it is economical to manufacture.
Filters of the type with which the present invention is concerned are disclosed in U.S. Pat. Nos. 3,402,531 and 3,802,169, for example. In U.S. Pat. No. 3,402,531 a plurality of filter elements are adapted to be arranged in stacked relationship to provide a maximum filtration area in a minimum space for supply of filtered air to a locomotive diesel engine or the like. U.S. Pat. No. 3,802,169 and applicants' co-pending application Ser. No. 791,468, filed Apr. 27, 1977, disclose arrangements wherein a single filter element is positioned to filter air supplied to an engine or the like.
The tapered dual element filter of the present invention is capable of use in either of the environments in U.S. Pat. Nos. 3,402,531 and 3,802,169, and when used as a single filter element on a truck engine, for example, is of sufficient strength and ruggedness to support the weight of a man thereon. For example, during service on heavy machinery and equipment such as trucks and the like, mechanics frequently step on top of the air filter, and the filter must thus not only be capable of efficiently filtering air supplied to the engine, but must also be capable of supporting the weight of the man. Alternatively, when a plurality of the filters according to the invention are stacked one upon the other and used in an environment such as in U.S. Pat. No. 3,402,531, a simple and efficient filter structure is obtained which has a relatively large open area for minimum impedance to flow of air therethrough.
The prior art filters, while serving the purpose for which they are designed, do not possess the economy of construction and strength along with the necessary large filtration area in a minimum amount of space as provided by the present invention.